ProxyFactoryBean does not work with prototype advisors/interceptors

Details

Description

There are several issues in the ProxyFactoryBean which prevent it from correctly creating beans with prototype advisors:

-Cannot create proxy when using prototype advisor when singleton=false
-Cannot create proxy when using prototype interceptor when singletone=false
-Cannot create proxy when using singleton target and singleton=false (ie, to use a prototype advisor on a singleton target)

Essentially, at the moment the only part of a prototype ProxyFactoryBean which may be a prototype is the target bean.

When trying to use a prototype the following exception is thrown:

BeanCreationException: Error creating bean with name 'prototypeTestBeanProxySingletonTarget' defined in class path resource [proxyFactoryTests.xml]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: TargetSource specified more than once: Specify in targetSource property or at the END of the interceptorNames list
...

Note that in targetSource is not actually specified more than once.

The main defect is that when the factory is initialized, it avoids loading prototype beans which appear in the interceptorNames property in order to improve performance. Instead it substitutes a null value. When this null value is later examined, it cannot be determined whether the bean was supposed to be a target or an advisor.